A wide variety of improvements have been made in recent years in the eyewear field, particularly with respect to eyewear intended for use in active sports or as fashion sunglasses. These improvements have been incorporated into eyewear having a unitary lens, such as the "Blades.RTM." design (Oakley, Inc.) the "M Frame.RTM." line (Oakley, Inc.), and the "Zero.RTM." line also produced by Oakley, Inc. These eyewear designs accomplish a variety of functional advantages, such as maximizing interception of peripheral light, reducing optical distortion and increasing the wearer's comfort level, compared to previous active sport eyewear.
The unitary lens of the "Blades.RTM." eyewear incorporates the cylindrical geometry disclosed, for example, in U.S. Pat. No. 4,859,048, issued to Jannard This geometry allows the lens to closely conform to the wearer's face and intercept light, wind, dust, etc. from directly in front of the wearer (anterior direction) and peripherally (lateral direction). See also U.S. Pat. No. 4,867,550 to Jannard (toroidal lens geometry).
Although the early unitary lens systems provided a full side-to-side range of vision and good lateral eye protection, the potential for optical distortion still exists. In a unitary lens system, for example, the angle of incidence from the wearer's eye to the posterior lens surface changes as the wearer's sight line turns in either the vertical or horizontal planes. This results in disparate refraction between light entering closer to the front of the lens and peripheral light entering at the lateral ends. To address this source of prismatic distortion, U.S. Pat. No. 4,859,048 discloses tapering the thickness of the lens from the medial portion toward the lateral edge.
Unitary lens protective helmet shields are subject to the same sources of optical distortion. A wide variety of helmet shields are known for such activities as motorcycle riding, football, lacrosse, hockey and the like. While the state of the art in each of these applications has generally achieved the desired level of physical eye protection, the current products generally still exhibit relatively high prismatic distortion and sometimes also power and/or astigmatism.
Another class of eyewear known as goggles often employ unitary lenses. Goggle applications include skiing, motocross, underwater diving masks, and a variety of industrial safety applications such as welding and for power equipment operators. Typically, goggles offer sealed protection to the eyes and adjacent areas of the wearer's face against particulate matter or water, without providing full head protection. As with helmets, goggle designs have tended to achieve good protection at the expense of introducing prismatic distortion, power and/or astigmatism.
One additional factor which affects vision through goggles is fogging. Because the wearer's face is usually warmer than the surrounding atmosphere for most applications (particularly for skiing and diving), the goggle lens is often colder than air trapped between the wearer's face and the lens. Moisture in the trapped air (e.g., from the wearer's sweat) thus tends to condense upon the inside of a goggle lens. Indeed, in extremely cold conditions, as often encountered in skiing applications, condensed moisture can even freeze upon the lens, clouding vision considerably.
One solution to this problem is to vent moisture from the wearer's side of the goggle lenses to the outside of the lens. This solution is, of course, impractical for diving applications. Even for skiing, however, providing ventilation risks allowing wind, snow, hard ice particles, etc. to enter the goggles, counter to the purpose for the goggles. Accordingly, any ventilation for the purpose of defogging must be minimized to prevent injury to the wearer.
Another solution to the problem of fogging in goggles is to provide insulation between the lens surface closest to the wearer's face and the cold outside atmosphere. Double lens structures, having spaced inner and outer lenses, provide such insulation in many goggle designs. Exemplary prior art double lens goggles are disclosed in U.S. Pat. Nos. 3,377,626; 3,591,864; and 4,571,748. The double lens insulated structure has also been applied to dual lens goggles, with each of a left lens and right lens including inner and outer lenses, as disclosed in U.S. Pat. No. 5,428,411.
While ventilation and/or double lens structures may reduce fogging, such structures do not address and may exacerbate optical distortion through the lenses. Accordingly, there remains a need for a nonprescription goggle which can protect a wearer's eyes from harmful light, wind and particles while at the same time minimize optical distortion throughout both a vertical and horizontal angular range of vision.